Note: Descriptions are shown in the official language in which they were submitted.
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FLAME-RETARDANT CELLULOSE ESTER PREPARATIONS
The present invention relates to cellulose ester preparations comprising
phosphorus-containing
propionic acid derivatives as flame-retardant plasticizers.
Esters of cellulose with short-chain aliphatic carboxylic acids have long been
used industrially as
engineered/engineering materials. Typical examples of these cellulose esters
are cellulose acetate,
cellulose propionate, cellulose butyrate and also mixed esters, such as
cellulose acetate propionate
or cellulose acetat butyrate. Their methods of making and processing are
known, for example from
K. Balser, L. Hoppe, T. Eicher, M. Wandel, H.-J. Astheimer and H. Steinmeier:
"Cellulose Esters",
Ullmann's Encyclopedia of Industrial Chemistry Release 2005, Electronic
Release, 7th ed., chap. 2
("Organic Esters"), Wiley-VCH, Weinheim 2005.
Cellulose esters are processible into thermoplastic moulding compounds, foams,
sheets, films,
coatings, paints and fibres. Plasticizers are frequently added in order to
improve the mechanical
properties of the engineering/engineered material and to lower the processing
temperature.
There are some applications, for example in the electrical and electronics
sector, where the
products formed from plasticized cellulose ester preparations are expected to
comply with certain
flame-retardancy requirements. This is typically accomplished by using a
plasticizer which is also a
flame retardant. Prior art examples of such flame-retardant plasticizers are
aryl phosphates, such as
triphenyl phosphate (cf. US 1,981,312) or resorcinol bis(diphenyl phosphate)
(cf. WO 9205219
Al), alkyl phosphates, such as triethyl phosphate (cf. US 2,617,737) or
alkylene bis(phosphate)s
(cf. US 2,782,128) and chloroalkyl phosphates, such as tris(chloroethyl)
phosphate (cf. US
2,618,568), or halogenated phthalic esters (cf. US 2,062,403).
Aryl phosphates and particularly triphenyl phosphate are of outstanding
importance here because,
as well as flame retardancy, they confer further useful properties on a
cellulose ester preparation,
for example a reduced rate of water vapour transmission (cf. US 2003/0118754
Al). However,
prior art flame-retardant plasticizers have certain disadvantages. To wit, the
compatibility of aryl
phosphates with cellulose esters is limited. One possible consequence is that
the plasticizer exudes
from the cellulose ester preparation. To control exudation, aryl phosphates
often have to be used
together with traditional plasticizers, which do not have any flame-retardant
properties. Plasticizing
alkyl phosphates often also have excessive volatility, reducing for example
the dimensional
stability of products made from the cellulose ester preparation.
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A further disadvantage with the flame-retardant plasticizers known from the
prior art is considered
to be their potentially disadvantageous effect on man and the environment.
Triphenyl phosphate is
very toxic to aquatic life with long-lasting effects (GHS classification
H410). Tris(chloroethyl)
phosphate is suspected of causing cancer (GHS classification H351). Brominated
plasticizers, for
example tetrabrominated bis(2-ethylhexyl) phthalate, are suspected of
persistence and
bioaccumulation. Cellulose ester preparations comprising such plasticizers are
less and less
accepted in consumer applications.
There is accordingly a need for flame-retardant plasticizers that are highly
compatible with
cellulose esters, and do not contain any halogen compounds or any aryl
phosphates. Typical
properties of plastics based on cellulose esters, for example transparency and
light-fastness, should
ideally be affected as little as possible.
US 4,137,201 already discloses cellulose ester preparations containing a
thermal stabilizer
comprising a combination of certain 9,10-dihydro-9-oxa-10-phosphaphenanthrene
10-oxide
derivatives, antioxidants and acid-binding epoxy compounds.
These thermal stabilizers are employed in amounts of 0.10 to 1.0 part,
preferably 0.10¨ 0,30 part,
based on 100 parts of cellulose ester. Thermal stabilizers are substances that
are incorporated in
plastics compositions in order to counteract degradation of the aesthetic or
mechanical properties of
these plastics compositions due to heat during the product life cycle.
The problem addressed by the present invention is that of providing a flame-
retardant plasticized
cellulose ester preparation that overcomes the prior art disadvantages
referred to.
It was found that by using certain, phosphorus-containing propionic acid
derivatives, it is possible
to provide cellulose ester preparations that have flame-retardant properties
in addition to being
plasticized. Surprisingly, the novel cellulose ester preparations require no
additional plasticizers
and attain a level of flame retardancy equivalent to that of the prior art
without any need for
halogen compounds or aryl phosphates.
The present invention accordingly provides a cellulose ester preparation
characterized in that it
contains
a) at least one cellulose ester, and
b) at least one phosphorus-containing propionic acid derivative of formula (I)
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0
P\ A¨ Z
X
0
(I),
where
X represents oxygen or sulphur, preferably oxygen,
= represents hydrogen or methyl, preferably hydrogen,
A represents oxygen or NH, preferably oxygen,
= represents an n-valent saturated, straight-chain or branched, aliphatic
hydrocarbyl
moiety of 1 - 20 carbon atoms which is optionally interrupted by one or more
heteroatoms from the series oxygen and sulphur, or an n-valent 5- or 6-
membered
heterocyclic ring which contains one to three nitrogen atoms as heteroatoms
and is
optionally substituted by one or more identical or different substituents,
and
represents an integer from 1 to 4.
Possible substituents for the optionally substituted n-valent 5- or 6-membered
heterocyclic ring Z
are preferably CI-C.4 alkyl moieties, in particular methyl and ethyl, CI-CI
alkoxy moieties, in
particular methoxy and ethoxy, and CI-C.4 alkylene moieties, in particular
methylene and ethylene.
The cellulose ester preparation of the present invention preferably contains
at least one phosphorus-containing propionic acid derivative of formula (I)
where
= represents an n-valent saturated, straight-chain or branched, aliphatic
hydrocarbyl
moiety of 1 to 10 carbon atoms which is optionally interrupted by one to four
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heteroatoms from the series oxygen and sulphur, or an n-valent 5- or 6-
membered
heterocyclic ring which contains one to three nitrogen atoms as heteroatoms
and is
optionally substituted by one to three identical or different substituents.
The cellulose ester preparation of the present invention more preferably
contains
at least one phosphorus-containing propionic acid derivative of formula (1)
where
represents an n-valent saturated, straight-chain or branched, aliphatic
hydrocarbyl
moiety of 1 to 6 carbon atoms which is optionally interrupted by one or two
oxygen atoms, or an n-valent 5- or 6-membered heterocyclic ring which contains
1 0 one to three nitrogen atoms as heteroatoms and is optionally
substituted by one to
three identical or different substituents.
In the very particularly preferred embodiments (la) to (1d), the cellulose
ester preparation of the
present invention contains at least one phosphorus-containing propionic acid
derivative of
formula (1) where the moieties X, R, A and Z and the index n each have the
meanings specified for
the particular embodiment in the following table:
Embodiment X R A
(la) 0 0 methyl, ethyl, n-propyl, isopropyl, n-
butyl,
isobutyl, 2-ethylhexyl, isooctyl, n-nonyl,
isononyl, 2-propylheptyl, n-decyl or isodecyl
(lb) 0 H 0 -CH2CH7-, -CH2CH2CH2-, -CH7CH(CF13)- 2
, -CH2CH2CH2CH2-, -CH2CH2CH(CH3)-
, -CH?C(CH3)2CF12-, -
CH,CH2CH2CH2CH2CH2- or -CH2CH,-0-
CH2CH2-
(1c) 0 H 0
(-CH2)3CCH3 or 3
1,3,5-tris(ethylene)-1,3,5-triazine-2,4,6-trione
(1d) 0 H 0 (-CH2)4C 4
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The cellulose ester preparation of the present invention may contain the
phosphorus-containing
propionic acid derivatives of formula (I) individually or in any desired
mixture. Some of the
formula (I) propionic acid derivatives present in the cellulose ester
preparation of the present
invention are known (cf. for instance DE-A 26 46 218 and Organic Letters 2005,
Vol. 7, No. 5,
Supplementary Information S8).
The phosphorus-containing propionic acid derivatives of embodiment (la), where
X represents
oxygen, R represents hydrogen, A represents oxygen, n represents 1 and Z
represents 2-ethylhexyl,
isooctyl, n-nonyl, isononyl, 2-propylheptyl, n-decyl or isodecyl in formula
(I), are novel and
likewise form part of the subject-matter of the present invention.
The phosphorus-containing propionic acid derivatives of embodiment (lb), where
X represents
oxygen, R represents hydrogen, A represents oxygen, n represents 2 and Z
represents -CH2CH2-
, -CH2CH(CH3)-, -CH2CH2CH2CH2-, -CH2CH2CH(CH3)-, -
CF2C(CH3)7CH2-
, -CFECH2CH,CH2CH2CH2- or -CH2CH2-0-CH2CH2- in formula (I), are likewise novel
and part of
the subject-matter of the present invention.
The novel and known propionic acid derivatives of formula (I) are useful as
flame-retardant
plasticizers for cellulose ester preparations. The present invention
accordingly also provides for the
use of phosphorus-containing propionic acid derivatives of formula (I) as
flame retardants with
plasticizing properties for cellulose ester preparations.
The novel and known phosphorus-containing propionic acid derivatives of
formula (I) where n
represents 1 are obtainable in a conventional manner, for example by the
methods described in
DE-A 26 46 218 and Organic Letters 2005, Vol. 7, No. 5, Supplementary
Information S8, e.g. by
reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide with appropriate
acrylic esters at a
temperature of 35 to 65 C under atmospheric pressure.
The starting 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide and acrylic
esters are
commercially available.
The novel and known phosphorus-containing propionic acid derivative of
formulae (I) where n
represents 2, 3 or 4 are obtainable in a similar manner by reacting 9,10-
dihydro-9-oxa-10-
phosphaphenanthrene 10-oxide with the acrylic esters of appropriate bi-, tri-
or tetravalent polyols,
as for example known from European Polymer Journal, 2011, Volume 47, pages
1081 - 1089.
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The cellulose esters present in the cellulose ester preparation of the present
invention preferably
comprise cellulose acetate, cellulose triacetate, cellulose propionate,
cellulose butyrate, cellulose
acetate propionate or cellulose acetate butyrate, cellulose acetate phthalate,
carboxymethylcellulose
acetate, carboxymethylcellulose butyrate or a preparation from mixtures of
these cellulose esters. It
is particularly preferable for a cellulose acetate preparation.
The degree of substitution (DS) of the cellulose esters is 1.0 - 3.0 acyl
groups per anhydroglucose
unit. DS is quantifiable by methods known to a person skilled in the art, for
example by titrating
the esterified acyl groups as per ASTM D 871-96 and computing the DS from the
acyl group
content.
The preparation according to the present invention preferably concerns a
cellulose acetate
preparation having a degree of substitution in the range from 2.0 to 3.0
acetyl groups per
anhydroglucose unit.
The preparation according to the present invention contains in general 5 - 60
parts by weight of
phosphorus-containing propionic acid derivatives of formula (I) based on 100
parts by weight of
cellulose ester. Preferably, the preparation according to the present
invention contains 10 - 50 parts
by weight of the phosphorus-containing propionic acid derivative of formula
(I) based on 100 parts
by weight of cellulose ester.
The cellulose ester preparation of the present invention may optionally
further contain one or more
auxiliary and/or added-substance materials, or else not in any one particular
case. Such auxiliaries
or added-substance materials include for example:
1. Plasticizers, for example alkyl esters of benzoic acid, phthalic acid,
terephthalic acid,
cyclohexane-1,2-dicarboxylic acid, trimellitic acid, succinic acid, adipic
acid, sebacic acid,
azelaic acid, citric acid, acetylcitric acid, phosphoric acid, alkylene esters
of benzoic acid,
isosorbitol esters; polyesters obtainable from diols, dicarboxylic acids and
optionally
monools and monocarboxylica acids; epoxidized fatty acid esters, glycerol
esters of acetic
acid and fatty acids, phenyl esters of alkanesulphonic acids, or mixtures
thereof.
2. UV stabilizers, for example benzotriazoles, triazines,
hydroxybenzophenones,
benzoxazinones, resorcinol monobenzoates, salicylates, cinnamic acid
derivatives,
oxanilides, hydroxybenzoic esters, sterically hindered amine light absorbers
("HALS"), or
mixtures thereof.
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3. Thermal stabilizers and/or antioxidants, for example sterically hindered
phenols, sterically
hindered amines, epoxides of natural oils, organic phosphites, or mixtures
thereof.
4. Colorants, for example soluble dyes, organic pigments, inorganic
pigments, or mixtures
thereof.
5. Fillers, for example inorganic fillers based on silicon dioxide,
aluminium oxide, aluminium
oxide hydroxide, boehmite, silicates, talc or organic fillers based on wood or
vegetable
fibres, or mixtures thereof.
6. Polymers, for example polyacrylates, polymethacrylates, ethylene-
vinyl acetate copolymers,
or mixtures thereof.
7. Blowing agents, for example physical blowing agents such as carbon
dioxide, nitrogen,
propane, butane, pentane, ethanol, propanol or chemical blowing agents such as
citric
acid/bicarbonate mixtures.
8. Scents, biocides, pesticides, processing aids and/or lubricants.
9. Flame retardants, for example those from the series of
1 5 a) organic phosphorus compounds, for example triethyl phosphate,
aliphatic bisphosphates,
dimethyl methanephosphonate, diethyl ethanephosphonate, dimethyl
propanephosphonate,
oligomeric phosphates or phosphonates, hydroxyl-containing phosphorus
compounds, 5,5-
dimethy1-1,3,2-dioxaphosphorinane 2-oxide derivatives,
614-
dibenzo[c,e][1,2]oxaphosphorine 6-oxide derivatives, e.g. N1,N2-bis(6-oxido-6H-
dibenzo[c,e][1,2]oxaphosphorin-6-y1)-1,2-ethanediamine, phosphazenes,
b) organic and inorganic, salt-type phosphorus compounds, for example
ammonium phosphate,
ammonium polyphosphate, ethylenediamine phosphate, melamine phosphate,
melamine
polyphosphate, metal-melamine polyphosphates, metal salts of dialkylphosphinic
acids,
metal salts of alkanephosphonic acids,
c) nitrogen compounds, for example melamine, melamine cyanurate, and
e) inorganic flame retardants, for example aluminium hydroxide,
boehmite, magnesium
hydroxide, expandable graphite or clay minerals.
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The cellulose ester preparation of the present invention is obtainable by the
familiar methods of
processing cellulose esters. It is for example obtainable in a procedure
wherein the cellulose ester,
the phosphorus-containing propionic acid derivative of formula (I) and
optionally one or more
auxiliary and/or added-substance materials are intimately mixed, preferably at
a temperature of 0 to
100 C, and the resulting mixture is then homogenized, preferably at a
temperature of 100 to 280 C.
Homogenization may utilize the customary assemblies, for example single- or
twin-screw
extruders, rolls or kneaders. The cellulose ester preparation thus obtained
may be granulated,
pelletized or otherwise formatted in further processing steps.
In an alternative method of production, the components of the cellulose ester
preparation are
homogenized in the presence of a solvent. Suitable solvents are methanol,
ethanol, isopropanol,
acetone, butanone, ethyl acetate, butyl acetate, dichloromethane, toluene and
mixtures thereof.
The as-obtained solution is directly usable for production of thermoplastic
films, sheets, coatings
and paints. The as-obtained solution may for example be converted to any
desired form, for
example as liquid film spread out over a surface or distributed in a three-
dimensional body. The
solvent evaporates to leave a thermoplastic cellulose acetate film in the
shape of this surface or
three-dimensional mould.
The solutions thus obtained likewise form part of the subject-mater of the
invention. The solutions
of the present invention preferably contain at least one organic solvent, in
particular at least one
organic solvent selected from the series methanol, ethanol, isopropanol,
acetone, butanone, ethyl
acetate, butyl acetate, dichloromethane and toluene.
The cellulose ester preparation of the present invention is further
processible by the familiar
methods of processing thermoplastic materials, for example to produce flame-
retarded mouldings,
sheets, films, coatings, paints and fibres. It is preferably further processed
by extrusion or injection
moulding. It is likewise preferable to process same by pressing whereby a
homogeneous mixture of
the recited constituents, for example in the form of sheets or hides, is
thermoformed under pressure
into a desired shape. By using a press, this method is capable for example of
producing sheet
products of defined thickness. By using the abovementioned blowing agents,
methods known
per se can be used to produce foams.
The present invention further provides the use of cellulose ester preparations
according to the
present invention in the manufacture of flame-retarded mouldings, sheets,
films, coatings, paints
and fibres, and also the mouldings, sheets, films, coatings, paints and fibres
thus obtained, and
further-processing products thereof.
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The extrusion- or injection-moulded articles, solid sheet products, cellular
sheet products, sheet
foams, sheets, films, coatings, paints and fibres thus obtained are used in
the electrical and
electronics sector, for example in housing parts, switches or plugs, in civil
engineering, for
example as insulants, and in vehicle construction, for example in interior
trim, sill plates, foot mats,
trunk carpets, seat covers, carbody parts, spoilers or exterior trim strips.
The present invention further provides the use of mouldings according to the
present invention in
the manufacture of housing parts switches, plugs, insulants, interior trim,
sill plates, foot mats,
trunk carpets, seat covers, carbody parts, spoilers or exterior trim strips.
Embodiments of the invention will now be more particularly described by way of
example in that
they shall not be construed as limiting the invention.
Examples
Parts hereinbelow are by weight.
Preparing the phosphorus-containing propionic ester of formula (I) where X =
0, R = H, A =
0, Z = n-butyl and n = 1
n-Butyl 6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorine-6-propionate was prepared as
per the method
of Organic Letters 2005, Vol. 7, No. 5, Supplementary Information S8, by
reacting 6H-
dibenzo[c,e][1,2]oxaphosphorine 6-oxide with n-butyl acrylate to obtain a
colourless liquid having
a viscosity of 6500 mPas at 23 C.
Production of cellulose ester preparations
Table 1: Raw materials used for production of cellulose ester
preparations
Component Designation Description
A cellulose acetate crude cellulose acetate, unmodified, DS
= 2.5 acetyl
groups per anhydroglucose unit.
Vulkanox BHT antioxidant
acetone solvent
Fl Disfiamoll TP triphenyl phosphate, flame retardant
and plasticizer,
from Lanxess
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F2 Levagare TP LXS 51078 phosphate ester preparation based on
diethylene glycol
bis(diethyl phosphate), flame retardant and plasticizer,
from Lanxess
F3 RDP resorcinol bis(diphenyl phosphate),
flame retardant and
plasticizer, from Yoke
F4 Uniplex FRP 45 tetrabrominated bis(2-ethylhexyl)
phthalate, flame
retardant and plasticizer, from Lanxess
F5 phosphorus-containing flame retardant and plasticizer,
prepared as described
propionic ester of above
formula (I) where X = 0,
R = H, A = 0, Z = n-butyl
and n =
Production of solutions of cellulose ester preparations
Solvent, flame retardant and antioxidant as per table 1 are initially charged
in a glass flask in the
quantitative ratios reported in table 2. As the glass flask is gently heated
to about 40 to 50 C in a
water bath, the cellulose acetate powder quantity reported in table 2 is added
with constant stirring
to prevent formation of gel clumps. The solution obtained after about 5 hours
is clear, free from
particles and useful for production of cast sheets.
Processing of cellulose ester preparation into sheets
About 150 g of the solution are poured into a horizontal 20 x 20 cm casting
mould open at the top.
The solvent is evaporated slowly, over a period of not less than one day. The
sheet formed is
removed from the mould and dried in a hot air oven at 60 to 70 C to remove
residual solvent. The
drying process can take several hours. It is complete once the sheet samples
are solvent-free, i.e.
stop losing weight.
Test specimens, for example dumbbell shapes, are die-cut out of the cellulose
ester sheets. The test
specimens were homogeneous, i.e. bubble-free and of uniform thickness. The
test specimens are
preferably taken from the centre of the sheet.
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Processing of cellulose ester preparation by thermoforming
An hydraulic press is used to thermoform cellulose ester sheets at 170 - 180 C
into 2 mm thick,
transparent and bubble-free sheet products. Test specimens for flammability
tests by the UL 94
method are sawn from the sheet products.
Determination of flame retardancy
The cellulose ester preparations are tested for fire resistance by the method
of UL 94 ("Standard
Test for Flammability of Plastic Materials for Parts in Devices and
Applications" of Underwriters
Laboratories). Five test specimens measuring about 125 * 12.5 * 2.0 mm are in
each case clamped
vertically into a holder and subjected in succession to two applications of a
small burner flame. No
test specimen shall burn to the holding clamp.
If the sum total of the burning times after flame application in a series of
five test specimens from
one recipe is less than 50 s, no test specimen has a burning time of more than
10 s after flame
application, no test specimen has an afterglow time of more than 30 s and no
test specimen drips
flaming particles, then the recipe is assigned to the class V-0.
If the sum total of the burning times after flame application in a series of
five test specimens from
one recipe is less than 250 s, no test specimen has a burning time of more
than 30 s after flame
application, no test specimen has an afterglow time of more than 60 s and no
test specimen drips
flaming particles, then the recipe is assigned to the class V-1.
If the sum total of the burning times after flame application in a series of
five test specimens from
one recipe is less than 250 s, no test specimen has a burning time of more
than 30 s after flame
application, no test specimen has an afterglow time of more than 60 s but the
specimens drip
flaming particles, then the recipe is assigned to the class V-2.
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Test results for cellulose ester preparations
Table 2: Composition (parts by weight) and test results of Inventive
Example B1 and of
non-inventive Comparative Examples V1 to V4 for cellulose ester
preparations.
Example V1 V2 V3 V4 B1
A 70 70 70 70 70
0.3 0.3 0.3 0.3 0.3
270 270 270 270 270
Fl 30
F2 30
F3 30
F4 30
F5 30
UL 94 class V-2 none none V-2 V-2
ash residue (%) 4.6 18.5 20.2 6.1 28.1
Shore D 69.6 65.4 77.5 68.7 78.3
Determination of tensile strength
The determination is carried out in accordance with DIN EN ISO 527 on a Lloyd
tensile tester with
laser extensometer using in each case five S 2 dumbbell specimens die-cut out
of sheets.
Determination of Shore hardness
The determination is carried out using a Zwick durometer in accordance with
the manufacturer's
instructions for the T 48 electronic unit. For measurement, the sheets were
stacked together to form
test specimens about 5 mm in thickness.
Determination of sheet homogeneity
Sheet homogeneity was determined by comparing the sheets in respect of
transparency, streaks,
uniformity of thickness and surface texture. The qualitatively best sheet is
ranked 1, the worst 5.
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Determination of light transmission
The light transmission of the sheets was investigated using a Lambda 12 UV/VIS
spectrometer
from Perkin Elmer. Transmission was measured here in per cent in 2011111 steps
from 400 to
1100 nm. The transmissions measured across the full wavelength range were
averaged and the
average transmission value was used for comparing the individual sheet
samples.
Determination of thermal ageing
Thermal ageing was determined in a Mathis oven at 200 C. The sheet test
specimens were
evaluated after 50 min in the oven. Since some sheets were deformed and
nonuniformly
discoloured after ageing, no colorimetric measurement could be carried out.
Instead, the test
specimens were ranked according to increasing discoloration. The least
discoloured sheet is ranked
1, the most discoloured sheet 5.
Determination of UV ageing
The UV ageing test was performed on the sheets in a Suntest CPS + at 500 kJ/m2
for 48 hours. A
Minolta Chromameter CR 400 was used for evaluation. The L a b values of the
sheet samples were
measured before and after ageing. The colour change was determined as ((L, ¨
E0)2 + (at ¨ ao)2
(bt ¨ b0)2) 5
Determination of thermal stability by DSC
The thermal stability of the cellulose ester preparations was determined using
DSC. Sheet samples
were heated under nitrogen from room temperature to 500 C at a rate of 10
C/min. The onset of
any significant reaction/degradation of the material was taken to be the first
significant peak above
the typical processing temperature of about 200 C for cellulose esters.
Determination of thermal stability by TGA
The thermal stability of the cellulose ester preparations was determined using
TGA. Sheet samples
were heated under nitrogen from room temperature to 500 C at a rate of 10
C/min. Above their
processing temperatures, the cellulose ester preparations start to undergo
degradation reactions
which lead to weight loss. The weight loss at 305 C was chosen as basis for
comparing stability.
Determination of ash residue
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The ash residue is determined by weighing sheet samples before and after
storage in a muffle kiln.
To this end, sheet samples are weighed into a porcelain crucible, placed in
the muffle kiln at 500 C
for one hour and then reweighed.
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Table 3: Composition (parts by weight) and test results of Inventive
Example B2 and of
non-inventive Comparative Examples V5 to V8 for cellulose ester
preparations.
Example V5 V6 V7 V8 B2
A 30 30 30 30 30
B 0.5 0.5 0.5 0.5 0.5
C 168 168 168 168 168
Fl 15
F2 15
F3 15
F4 15
F5 15
tensile strength (N/mm2) 32.5 17.4 32.6 9.6 26.8
Shore A 100 99 99 88 97
sheet homogeneity
2 1 4 5 3
(ranked by quality)
light transmission (%) 82 64 2.9 1.2 90
thermal ageing
2 5 1 3 4
(ranked by quality)
colour change after UV ageing 18 7.4 29 52 5.3 '
thermal stability by DSC
330 290 318 339 336
(peak in C)
thermal stability by TGA
23.7 75.2 8.1 18.9 14.1
(weight loss in %)
ash residue (%) 1.0 2.8 2.2 0.0 2.1
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Evaluation of results
All the Fl to F5 plasticizer-cum-flame retardants tested were highly
compatible with cellulose
acetate. The cellulose acetate preparations obtained therefrom were readily
processible into films
and, by thermoforming, into sheet products. The test results in tables 2 and 3
make it possible to
compare the Inventive Cellulose Ester Preparations based on F5 with the prior
art preparations
based on Fl (triphenyl phosphate, cf. US 1,981,312), F2 (phosphate ester
preparation based on
diethylene glycol bis(diethyl phosphate), cf. US 2,782,128), F3 (resorcinol
bis(diphenyl
phosphate), cf. WO 9205219 Al) and F4 (tetrabrominated bis(2-ethylhexyl)
phthalate, cf. US
2,062,403).
Fire properties:
According to table 2, Inventive Cellulose Ester Preparation BI, comprising the
phosphorus-
containing propionic acid derivative of formula (I), achieves the UL 94 class
V-2. This means that
B1 exhibits the same level of flame retardancy as Comparative Examples V1,
comprising Fl
(Disflamolf TP), and V4, comprising F4 (Uniplex FRP 45).
Thermal stability:
As is apparent from table 3, Inventive Cellulose Ester Preparation B2,
comprising the phosphorus-
containing propionic acid derivative of formula (I), exhibits surprisingly
high stability on heating.
The DSC shows a decomposition peak at a temperature that is higher than that
of the
decomposition peak of preparation V5, comprising Fl (Disfiamoll TP), and is
only exceeded by
V8, comprising F4 (Uniplex FRP 45), by 3 C.
The TGA shows Inventive Cellulose Ester Preparation B2, comprising phosphorus-
containing
propionic acid derivative of formula (I), to have a relatively low 305 C
weight loss, only
preparation V7, comprising F3 (RDP), being superior in this respect.
Other properties:
Inventive Cellulose Ester Preparation B2, comprising the phosphorus-containing
propionic acid
derivative of formula (I), processes into a transparent film, and shows the
highest light transmission
of all the preparations tested. Of all the preparations tested preparation B2
also exhibits the smallest
colour change after UV ageing.
CA 02921121 2016-02-17
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Summary:
What is surprising is the finding that the phosphorus-containing propionic
acid derivatives of
formula (I) act in the preparations of the present invention not just as flame
retardants, but at the
same time also as plasticizers. No addition of further plasticizers and/or
flame retardants is
required.
Cellulose acetate is thus easy to process with the phosphorus-containing
propionic acid derivative
of formula (I) into the cellulose ester preparations of the invention. These
preparations are free
from undesirable halogenated or aryl phosphate-containing plasticizers. At the
same time, their
physical properties are equivalent to and in some aspects even superior to the
properties of prior art
preparations.
Thus they achieve the same UL 94 flame-retardancy classification as cellulose
ester preparations
comprising Fl (Disflamoll TP) or F4 (Uniplex FRP 45). In addition, the
preparations according to
the present invention have high thermal stability. The surprisingly lower
level of discolouration
after UV ageing and the high transmissivity testify to the superiority of the
cellulose ester
preparations according to the present invention over the comparative
preparations in applications
calling for transparency.
